There are currently a variety of squeegee blades utilized in screen printing presses to induce ink to travel through a mesh screen onto a substrate to receive the ink. Conventional squeegee blades have proven to be less than adequate when utilized under conventional press set up parameters, which typically include relatively high downward force on the blade holder and less than optimal blade speeds for a given ink and printed image size. When printers attempt to run conventional blades in a screen printing press at significantly higher than conventional blade holder speeds, the result is typically degraded print quality on the printed substrate. One prior method printers have often utilized to attempt to improve squeegee speed and thereby screen printing efficiency has been to increase the downward pressure on the squeegee blade holder beyond conventional parameters. While, under certain very limited conditions, increased blade holder pressure can result in increased print speed and productivity, it more frequently results in degraded print quality and ink build up, which can increase press maintenance costs. Further, increasing downward pressure on the blade holder often leads to unacceptably high screen tearing rates and can further result in excessive wear on the squeegee blade, the screen and other printing press components. Still further, even when a screen printing press is set up with conventional blade holder downward forces and run at conventional speed, conventional blades are believed by the applicant to be less abrasion resistant and chemically stable than is optimal.
Furthermore, prior art squeegee blades often print a wavy ink film onto the substrate. In other words, the printed ink film deposited on the substrate frequently had an uneven, inconsistent thickness in both the y-axis and x-axis relative to the screen mesh. Moreover, both printing edges of the prior art squeegee blades tended to print similarly wavy ink films with similarly average thicknesses. For certain precision screen printing applications, such as printing high quality graphic design materials and printing membrane switches, the printing of consistent ink film thickness is of considerable importance. With conventional prior art squeegee blades, the best approach to attempting to print with a consistent film thicknesses was to slow print speeds far below optimal press throughput and, even then, significant numbers of the printed materials had to be rejected for failure to meet ink thickness or pin hole quality control standards.
U.S. Pat. No. 5,027,703 illustrates three examples of prior art squeegee blade design for use in manual screen printing presses. The first design, shown in FIG. 2, illustrates the most commonly used conventional rectangular blade. FIGS. 3-8 and FIGS. 9-10 of the '703 patent illustrate an internal profile and external profile squeegee blades, in which a cavity is located within the blade about ⅛ of an inch above the printing edge of the blade in order to allow a measured volume of ink to fill the cavity during a print stroke. None of the three styles of blades illustrated in the '703 patent are believed to overcome the printing efficiency, durability, film consistency, pin hole and chemical resistance issues of prior art squeegee blades.